Simon Willison’s Weblog

Deep Think in the Gemini app (via) Google released Gemini 2.5 Deep Think this morning, exclusively to their Ultra ($250/month) subscribers:

It is a variation of the model that recently achieved the gold-medal standard at this year's International Mathematical Olympiad (IMO). While that model takes hours to reason about complex math problems, today's release is faster and more usable day-to-day, while still reaching Bronze-level performance on the 2025 IMO benchmark, based on internal evaluations.

Google describe Deep Think's architecture like this:

Just as people tackle complex problems by taking the time to explore different angles, weigh potential solutions, and refine a final answer, Deep Think pushes the frontier of thinking capabilities by using parallel thinking techniques. This approach lets Gemini generate many ideas at once and consider them simultaneously, even revising or combining different ideas over time, before arriving at the best answer.

This approach sounds a little similar to the llm-consortium plugin by Thomas Hughes, see this video from January's Datasette Public Office Hours.

I don't have an Ultra account, but thankfully nickandbro on Hacker News tried "Create a svg of a pelican riding on a bicycle" (a very slight modification of my prompt, which uses "Generate an SVG") and got back a very solid result:

The bicycle is the right shape, and this is one of the few results I've seen for this prompt where the bird is very clearly a pelican thanks to the shape of its beak.

There are more details on Deep Think in the Gemini 2.5 Deep Think Model Card (PDF). Some highlights from that document:

• 1 million token input window, accepting text, images, audio, and video.
• Text output up to 192,000 tokens.
• Training ran on TPUs and used JAX and ML Pathways.
• "We additionally trained Gemini 2.5 Deep Think on novel reinforcement learning techniques that can leverage more multi-step reasoning, problem-solving and theorem-proving data, and we also provided access to a curated corpus of high-quality solutions to mathematics problems."
• Knowledge cutoff is January 2025.